Rinse the stain under cold running water as soon as possible, then treat it with an enzyme-based method before washing. Fresh blood comes out of most fabrics easily, while dried blood takes more effort but is still removable with the right approach. Here’s what works, why it works, and how to handle both fresh and set-in stains.
Why Cold Water Comes First
Blood is a protein-based stain. The conventional wisdom is that cold water prevents those proteins from bonding permanently to fabric fibers, while hot water “cooks” them in place, similar to how egg whites turn solid in a hot pan. Interestingly, one study published in The BMJ actually found hot water more effective at removing blood stains when combined with cleaning agents. But for that initial rinse, before you’ve applied anything, cold water is the safer bet. It loosens and flushes out as much blood as possible without any risk of setting the stain deeper into the fabric.
Hold the stained area under cold running water, rubbing the fabric gently against itself. You’ll see the water run pink, then gradually clear. This step alone can remove most of a fresh stain. Once the visible blood is flushed out, move on to a treatment method.
Treat Fresh Stains With What You Have
Several common household products break down blood proteins effectively. Pick whichever one you have on hand.
- Hydrogen peroxide (3%): Blood contains an enzyme called catalase that reacts with hydrogen peroxide, creating that familiar fizzing action. This reaction helps lift the stain out of the fibers. Dab or pour a small amount directly on the stain, let it fizz for a few minutes, then rinse. One caution: peroxide can fade dark fabrics. Peroxide-containing detergents have been shown to cause color loss in dyed cotton, so test a hidden spot first if your underwear is dark or brightly colored.
- Baking soda paste: Mix two parts baking soda to one part water and spread the paste directly over the stain. Leave it for up to 30 minutes, then rinse clean. This works well as a gentle option for delicate fabrics.
- Enzyme-based laundry detergent: Detergents labeled “bio” or “enzymatic” contain protease enzymes that break apart the protein structure of blood. Protease works by splitting the peptide bonds in hemoglobin, essentially dismantling the stain at a molecular level. Rub a small amount into the wet stain and let it sit for 15 to 30 minutes before washing.
- Bar soap or dish soap: Plain soap rubbed directly into a wet stain and worked into the fabric with your fingers can handle light, fresh stains surprisingly well.
How to Handle Dried Blood
Dried blood is harder to remove because the proteins have had time to bind to the fabric fibers, but it’s far from permanent. The key is rehydrating the stain first to make it treatable again.
Soak the stained area in cold water for at least 30 minutes, or longer for heavy stains. You can also apply a solution of one part glycerin, one part white dish soap, and eight parts cold water directly to the stain, then cover it with a damp cloth or paper towel. Keep the stain moist with the solution and let it sit, replacing the cloth as it absorbs the blood. This drawing action pulls the rehydrated stain out of the fabric.
For stubborn dried stains, unseasoned meat tenderizer is a surprisingly effective option. The powdered form contains bromelain, an enzyme derived from pineapples that breaks down proteins in the same way it softens meat. Research has confirmed that bromelain can use hemoglobin (the protein that gives blood its red color) as a substrate, actively breaking it apart. Mix the powder with a small amount of cold water to form a paste, apply it to the dampened stain, and leave it for 20 to 30 minutes. In testing, meat tenderizer didn’t just dilute blood stains the way plain water did. It actually transferred the blood out of the fabric entirely.
Washing and Checking Before Drying
After treating the stain, wash the underwear as you normally would. Check the stained area before putting it in the dryer. Heat from a dryer permanently sets any remaining blood proteins into the fabric, making the stain nearly impossible to remove afterward. If you can still see a faint mark, repeat the treatment and wash again. Air drying is always the safer choice until you’re sure the stain is completely gone.
Protecting Dark or Delicate Fabrics
Most underwear is dark cotton, often blended with spandex or elastane. These fabrics need a little extra consideration. Hydrogen peroxide and bleach-based products can strip color from dark dyes, particularly sulfur-based dyes commonly used in black cotton. If your underwear is black or a deep color, stick with enzyme detergent, baking soda paste, or the soap-and-cold-water method instead.
For lace, mesh, or other delicate materials, avoid aggressive scrubbing. Soak the fabric and let the cleaning agent do the work rather than grinding the fibers together. Enzyme-based treatments are ideal here because they break down the stain chemically without requiring physical force.
Quick Steps When You’re Not at Home
If you notice a stain at work, school, or anywhere without your full cleaning arsenal, head to a bathroom and run cold water over the fabric as soon as you can. Even just wetting the stain and blotting it with paper towels makes a significant difference. If there’s hand soap available, rub some into the stain and rinse. The goal isn’t perfection in the moment. It’s preventing the blood from drying and setting so you can treat it properly later. A stain that’s been rinsed, even partially, is dramatically easier to remove at home than one that’s been left to dry for hours.